With the increasing emphasis on energy efficiency, greatly expanded efforts have been made to recover the energy value of waste heat developed in industrial processes and also to recover the energy value of conditioned air which is exhausted from buildings or industrial processes. The energy represented in such conditioned air may be heat energy or the energy value represented by cooled air. That is, if the air supply is heated to a temperature above ambient or cooled to a temperature under ambient, the energy expended in heating or cooling such air if recovered will improve the efficiency of the conditioning process.
An example of such application is described in U.S. Pat. No. 4,173,924 of the present inventor and assigned to the same assignee as the present application, in which the air supplied to industrial paint spray booths is conditioned to a controlled temperature and humidity range, and the entire air flow is then exhausted to the atmosphere. The nature of such installation is such that enormous volumes of air flow must be conditioned and consequent enormous energy expenditures are required in heating or cooling the supply air.
In the aforementioned U.S. patent, the air exhausted from the paint spray booths is described as being highly filtered by a hydrodynamic filtration system disclosed in application Ser. No. 851,253, filed Nov. 14, 1977, now U.S. Pat. No. 4,222,319, and assigned to the same assignee as the present application. Such filtration system substantially eliminates paint overspray solids from the exhausted air, which in turn enhances the feasability of using air-to-liquid heat exchangers such as fin-on-tube coils through which the exhaust air from the paint spray booths may be passed in order to transfer heat out of or into any energy recovery system.
According to the energy recovery system disclosed in the aforementioned U.S. patent, heat is transferred into and out of the exhaust air flow during summer and winter conditions, respectively, upon circulation of the heat transfer liquid through the recovery coils or tubes and caused to be circulated over either the evaporator or condenser of a heat pump to thus efficiently recover relatively high proportions of the energy in such exhausted conditioned air.
While such air flow is substantially free from such overspray paint solids, 100% removal thereof is not possible. Given the enormous volume of air flow common in such systems, some accumulation of air solids of such heat recovery coils could be expected requiring regular maintenance in cleaning the coils in order to insure operation at an optimum degree of efficiency.
This is particularly necessary during summertime operation since the temperature differential from the incoming and ambient air is relatively slight, and a high degree of efficiency of the heat exchanger is required to enable transfer of sufficient heat energy into the coils.
It would be advantageous to increase the efficiency of such fin-on-tube coil arrangements for operation at relatively low temperature differentials thereacross.
The presence of slight concentrations of particulates has also led to the arrangement of an exhausting system including collecting of the exhaust flows from a number of such spray booths in a common chamber and the arrangement of a number of such fans drawing in air from the collection chamber and thence into an exhaust stack such as to direct the exhaust air upwardly at considerable velocity in order to disperse the overspray particulates remaining after filtration.
The aerodynamic efficiency of such arrangements has been affected by problems of flow distribution to such plurality of exhaust fans, since the intakes of such fans having been located at varying distances from the entrance location of the exhaust ducting.
Also, the outlets have commonly been arranged in a crossing pattern, creating considerable turbulent losses in the exhaust stack.
Sometimes it happens that difficulties are encountered in the operation of the filtration system such that a larger than normal concentration of paint solids are contained in the exhaust. In such cases, solid concentrations may reach levels resulting in the fouling of the energy recovery coils and it would be advantageous if in such installation of energy recovery coils these coils could be bypassed quickly such as to preclude such fouling.
Accordingly, it is an object of the present invention to provide an arrangement and installation for such energy recovery heat exchangers in an air exhaust flow in which maintenance and other cleaning operations on such coils are simplified.
It is yet another object of the present invention to provide such energy recovery coil installation in an exhaust system for paint spray booths of the type described, i.e., in which a plurality of exhaust fans are arranged about a collection chamber, the air flow being directed from such chamber into an exhaust stack or chimney.
It is still another object of the present invention to provide such exhaust system in which high aerodynamic efficiency of the exhaust flow is achieved.
It is another oabject of the present invention to provide an arrangement whereby the energy recovery coils may be readily bypassed in the event malfunction of the filtration system would result in damage to the energy recovery coils.
It is a further object of the present invention to provide an arrangement for such energy recovery coil in which a high degree of heat transfer efficiency is maintained.